1. Field of the Invention
A multi-compartment housing having means both to contain equipment in a cavity positioned within the housing, and to maintain a high pressure, relatively clean environment within the housing by a directed fluid flow through the housing around the cavity.
2. Description of Related Art
The protection of sensitive equipment in a hosthe environment is a continuing challenge to electrical and mechanical designers. Often this equipment can be extremely sensitive to the adverse effects of solid particulates, such as dust, that may be carried by a fluid atmosphere. These effects can include dust contamination of the equipment, or dust build up from an electrostatic charge, or the like; all potentially leading to early equipment failure or malfunction.
U.S. Pat. No. 5,086,422 for an OPTICAL DISK APPARATUS teaches the use of a U-shaped seal within a case to "keep dust from the optical parts", i.e., an optical pickup. The '422 Patent teaches that "dust contained in the atmosphere . . . or air" can be carried by "forced-air cooling" of the case. The seal taught by the '422 Patent guides this forced air toward selected heat sources within the case "to prevent the internal temperature of the optical disk apparatus from rising." However, the U-shaped seal has an open end at its downstream or lee side so that the optical pickup is exposed to the flow of forced air through the case. It would appear that any eddy currents in the flow of forced air at or near the lee side of the U-shaped seal could propel unwanted dust into the seal cavity around the optical pickup.
U.S. Pat. No. 4,306,835 for an AIR PURGING UNIT FOR AN OPTICAL PYROMETER OF A GAS TURBINE ENGINE teaches the use of a fluid screen adjacent to the exposed surface of an optical lens of the pyrometer. A sight tube, connected to the pyrometer unit, has a plurality of spaced and angled apertures at its mounted end which direct pressurized air into the sight tube to egress from its distal end. Thus the sight tube is an open-ended chamber with a dynamic flow of air through the chamber. It would appear that (1) this flow of air provides an opportunity for an electrostatic charge to build up on the optical lens, and (2) any unwanted solid particulates, such as dust, which may be carried by this flow of air could be attracted to and collect on the lens.